The present invention is related to improved processes and apparatus for forming internally enhanced tubing sometimes referred to in the art as internally grooved tubing, grooved tube, internally finned tube or tubing, and tubing provided with at least one internal spiral fin and the like.
As known to those skilled in the art, such internally enhanced tubing when used in heat exchanger applications is more advantageous than internally smooth tube because the internal spiral fins of the internally enhanced tubing provide greater thermal transfer between the tubing and heat transfer fluid flowing therethrough such as, for example, air conditioning fluid. As is further known, generally, the greater the height of the internal spiral fin, the greater the thermal transfer.
More particularly, the present invention is an improvement in the process and apparatus for forming spiral fins on the internal portion of relatively thin wall tubing which, as known to those skilled in the art, is notoriously difficult to do without rupturing, tearing, or shearing of the thin tubing wall or, if done by prior art processes and apparatus successfully, is notoriously slow and thus unwantedly expensive.
Further, the present invention is an improvement of the process and apparatus disclosed in U.S. Pat. No. 4,702,906, patented Oct. 27, 1987, entitled APPARATUS AND PROCESS FOR PROVIDING TUBING WITH AT LEAST ONE INTERNAL SPIRAL GROOVE OR FIN, Francis J. Fuchs, Jr. inventor (referred to hereinafter as the "Fuchs '096 Patent"). While the process and apparatus of the Fuchs '096 Patent have successfully formed spiral fins on the internal portion of thin wall tubing of certain heights, there still exists a need for improved processes and apparatus for forming such spiral fins of even greater heights.
Various processes and apparatus of forming internally enhanced tubing, other than that disclosed in the Fuchs '096 Patent, are also known to the art, for example, the process sometimes referred to as ring rolling, shear spinning, and the like, wherein tubing is placed over a forming member such as a mandrel or roller provided with external spiral ridges providing spiral grooves therebetween and external rollers are rolled over and around the tubing to deform or indent the internal portion of the tubing into the underlying spiral grooves provided in the forming member to produce the internal spiral fins.
While the above-noted prior art ring rolling, etc., process and equipment generally produce internally enhanced tubing having internal spiral fins of the desired height, such prior art equipment is relatively unwantedly expensive and the process practiced by such equipment is notoriously slow which adds further unwanted expense.
Accordingly, there exists a need in the art for less expensive equipment and an improved and less expensive process for forming internally enhanced tubing having internal spiral fins of sufficient height to provide the above-noted desired greater thermal transfer.